Respiratory disease gives rise to symptoms which are incapacitating. Often all symptoms of difficulty in breathing are lumped under the term, dyspnea, although several distinct sensations are present. This project investigates the mechanisms underlying specific respiratory sensations, using an unusual approach which combines psychophysics, respiratory physiology, and the study of unusual subjects such as ventilator-dependent quadriplegics, as well as normal and asthmatic subjects exposed to specific respiratory stimuli. This group has provided evidence that both lung volume and hypercapnia are perceived in the absence of chest wall afferents and has defined more precisely the use of descriptions for respiratory sensations. They propose to investigate the adaptation of sensation to prolonged hypercapnia and to discover whether an important component of respiratory discomfort can arise directly from sensory endings in the lung. They believe that knowledge of the fundamental properties of respiratory sensation will improve diagnosis and symptom relief, as has the study of pain.